Cigarette filters are made of bloomed cellulose acetate tow. Specifically, the cellulose acetate tow is a cellulose diacetate with a Degree of Substitution (D.S.) in the range of 2.0 to 2.6. The cigarette filter includes a filter element formed from the tow and wrapped with a plug wrap. Later, the cigarette filter may be attached to the wrapped tobacco column of a cigarette.
After the cigarette has been smoked, the cigarette filter (or butt) is discarded. If the butt is discarded improperly (e.g., thrown on the ground), it becomes an unsightly piece of litter. In recent years, more cigarette smokers have been forced to move outside to smoke. This effort has increased the amount of improperly discarded butts.
Cellulose acetate used in cigarette filters will degrade over time; the time to degrade, however, can be long (e.g., >4 year). Therefore, there is a need to accelerate the degradation of the cellulose acetate in butts.
Prior attempts have been made to accelerate the degradation of cigarette butts. These prior attempts to accelerate degradation involved adding a degradation promoting agent into the cellulose acetate tow during its manufacture. In U.S. Pat. Nos. 5,491,024 and 5,647,383, a photo-degradation agent, ultra fine titanium dioxide (TiO2), is added into the cellulose acetate tow during its manufacture. In U.S. Pat. Nos. 6,571,802 and 6,739,344, biodegradation promoting (or decomposition accelerating) agents and/or reaction controlling agents are added into the cellulose acetate tow during its manufacture. The biodegradation promoting agents include oxygen acid of phosphorus, oxygen acid of sulfur, oxygen acid of nitrogen, a partial ester of hydrogen salt of the foregoing acids, carbonic acid and its hydrogen salt, a sulfonic acid and a carboxylic acid.
There is still a need for degradable cigarette filters in which the degradation agents are not added into the cellulose acetate tow during its manufacture.